JP5928221B2 - Temper rolling method for cold-rolled steel sheet - Google Patents

Description

  The present invention relates to a method for preventing defects that are likely to occur when temper rolling cold-rolled steel sheets used in cans and automobiles.

  It is known that a defect called cross buckle or corrugation is likely to occur when temper rolling a cold rolled steel sheet. As a principle of occurrence of these defects, it is explained that the compressive load in the width direction generated during temper rolling is caused by buckling caused by being released on the roll bite exit side.

  And as for the countermeasures to date for the occurrence of these defects, as described in Patent Literature 1, the auxiliary roll on the exit side of the temper rolling mill is pushed up from the pass line to increase the outflow angle. Is disclosed.

  Further, as described in Patent Document 2, a method of reducing the stress in the width direction by increasing the mill exit tension or reducing the mill load is also disclosed.

JP 2001-259703 A JP-A-11-57804

  However, as described in Patent Document 1, when the outlet-side outflow angle is increased, warpage occurs due to the influence of tension bending. This warpage is offset by the weight of the steel plate if it is a thick steel plate, so it will not be a big problem, but if the steel plate is thin, such as a steel plate for cans, it will be an obstacle during processing. ,It becomes a problem.

  Further, as described in Patent Document 2, regarding the technique for adjusting the outlet side tension, the higher the tension, the more the occurrence of cross buckle can be prevented, but the equipment for obtaining the tension becomes large. Furthermore, in the case of the method of reducing the load, there arises a problem that the necessary steel sheet roughness cannot be secured if it is too low.

  The present invention has been developed in view of the above-described situation, and effectively prevents defects called cross buckles or corrugations that are likely to occur when temper rolling cold-rolled steel sheets used in cans and automobiles. It aims to provide a way to do.

That is, the gist configuration of the present invention is as follows.
1. When performing temper rolling at least twice on the cold-rolled steel sheet, when the second rolling from the end is performed by STD (A) and the final rolling is performed by STD (B),
The roll roughness difference of STD (A) with respect to STD (B) is ± 20% or less ,
The rolling load in STD (B) is 0.05 to 0.15 t / mm ,
The roll roughness of STD (B) is 1.4 to 1.8 times the product roughness,
A temper rolling method for cold-rolled steel sheets, wherein the rolling load of STD (A) is more than 0.15 t / mm .

  ADVANTAGE OF THE INVENTION According to this invention, the defect called the cross buckle or corrugation which is easy to generate | occur | produce when cold-rolling the cold-rolled steel plate used for a can, a motor vehicle, etc. can be prevented effectively.

It is a schematic diagram of a double type (tandem type) temper rolling mill. (a)-(c) is a figure explaining the form of the wavy shape defect which arises by temper rolling, respectively.

Hereinafter, the present invention will be specifically described.
In particular, the present invention applies temper rolling at least twice to cold-rolled steel sheets used in cans and automobiles. The contents will be described in the case of performing temper rolling twice as shown in FIG. At that time, when the first rolling is performed by the rolling roll: STD (A) indicated by reference numeral 1 in FIG. 1 and the final rolling is performed by the rolling roll: STD (B) indicated by reference numeral 2, STD The difference in roll roughness of STD (A) with respect to (B) is ± 20% or less and the roughness according to the product roughness, and the rolling load in STD (B) is 0.05 to 0.15 t / mm. It is characterized by that. In addition, in FIG. 1, the code | symbol 3 is a cold-rolled steel plate, and the arrow is a progress (rolling) direction of a steel plate.

In the present invention, when the roll roughness of STD (B) is used as a reference, it is desirable that the roll roughness of STD (A) is the same, but a difference within ± 20% is acceptable. . And the defect (henceforth a cross buckle etc.) called a cross buckle or corrugation can be effectively prevented by making rolling load in STD (B) 0.05-0.15 t / mm. It is.
In addition, the roughness in this invention has shown Ra: arithmetic mean roughness calculated | required based on the specification prescribed | regulated to JIS B 0601-2001.

  The above explanation is a case where a so-called tandem type rolling stand having two rolling stands as shown in FIG. 1 is used, but if it is a single stand, the first rolling is performed under the conditions of STD (A) according to the present invention. The second rolling may be performed under the conditions of STD (B) according to the present invention. If the temper rolling is performed in a rolling mill having three or more rolling stands, the second rolling from the end is performed. If the conditions of STD (A) according to the present invention are used and the final rolling is the conditions of STD (B) according to the present invention, the same effects as described above can be obtained.

  In the present invention, the roughness of the rolling roll, the roughness according to the product roughness means that the product roughness is within the allowable range of the target product roughness, specifically, The roll roughness difference of STD (A) with respect to STD (B) should be ± 20% or less, and the rolling load in STD (B) needs to be 0.05 to 0.15 t / mm. Above, it is preferable to adjust the rolling load by the rolling of STD (A) to obtain the target product roughness. At this time, the roll roughness of STD (B) is preferably 1.4 to 1.8 times the roughness of the product. The rolling load of STD (A) is preferably more than 0.15 t / mm, more preferably 0.7 t / mm or more.

The rolling load in the STD (A) may be appropriately determined depending on the type of steel sheet to be rolled and the surface roughness (product roughness) of the steel sheet, but as described above, if the range is 0.7 t / mm or more, This is preferable because the product roughness can be ensured.
When rolling 3 or more, there is no limitation on the roll roughness in the rolling before the second from the last, the rolling load of the second STD (A) from the last is sufficient, and the target product roughness In the case of reaching the degree, the rolling load is not particularly limited, but when the rolling load of the second STD (A) from the last is low and the target product roughness is not reached, the rolling load before the second from the last is reached. Also in rolling, the roll roughness difference with respect to STD (B) is preferably ± 20% or less, and the rolling load is preferably more than 0.15 t / mm, more preferably 0.7 t / mm or more.

  The product roughness may be set as appropriate according to the roughness required for the product, but the effect of preventing the cross buckle and the like in the present invention is a steel plate having a product roughness in the range of 2.5 to 3.5 μm. It is most effective against it. In order to achieve such product roughness, although it depends on other conditions such as the type of rolled steel sheet and the number of rolling, the roll roughness is preferably in the range of 4.4 to 5.4 μm.

Using the rolling rolls shown in FIG. 1, temper rolling was performed on steel sheets having a width of 850 mm, thickness: 0.22 mm, and rolling length direction: 10,000 m using the conditions described in Table 1. . The target product roughness was Ra of 3.2 μm (allowable range: 2.5 to 3.5 μm).
Moreover, the conditions described in Table 1 are the load and roll roughness of STD (A) and STD (B), and the roughness and visual evaluation of the product obtained as a result of the temper rolling are also described. .

After the temper rolling, visual inspection was performed to confirm the occurrence of defects such as corrugation shown in FIGS. 2A is a defect generally called an ear wave, FIG. 2B is a defect generally called a vertical stripe, and FIG. 2C is a defect generally called a bellows.
Here are the evaluation criteria:
○ ... Defects are not recognized during the predetermined rolling length. Δ ... Defects with a height of 150 µm or less are observed during the predetermined rolling length.
X: Defects with a height of more than 150 μm were observed.

  As shown in the table, test no. In all of the invention examples according to the present invention of 4 to 17, steel plates satisfying the target product roughness were obtained with almost no defects such as corrugation. In contrast, test no. In the comparative examples 1 to 3, it can be seen that corrugation occurs or the roughness of the obtained product cannot secure the target product roughness.

  Here, the above-described embodiment shows a case where a so-called tandem type rolling stand having two rolling stands is used. If a single stand is used, the first rolling is performed under the conditions of STD (A) in Table 1. The second rolling may be performed under the conditions of STD (B) in Table 1, and if it is temper rolling in a rolling mill having three or more rolling stands, the second rolling from the end is performed. If the conditions of STD (A) in Table 1 are set and the final rolling is set to the conditions of STD (B) in Table 1, the same effects as those of the above-described invention examples can be obtained. Moreover, even if the rolls of STD (A) and STD (B) are a plurality of rolls, there is no problem as long as each condition is satisfied.

1 Roll: STD (A)
2 Rolls: STD (B)
3 Cold rolled steel sheet

Claims (1)

When performing temper rolling at least twice on the cold-rolled steel sheet, when the second rolling from the end is performed by STD (A) and the final rolling is performed by STD (B),
The roll roughness difference of STD (A) with respect to STD (B) is ± 20% or less ,
The rolling load in STD (B) is 0.05 to 0.15 t / mm ,
The roll roughness of STD (B) is 1.4 to 1.8 times the product roughness,
A temper rolling method for cold-rolled steel sheets, wherein the rolling load of STD (A) is more than 0.15 t / mm .

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